1. Field of the Invention
The present invention relates to an improved guide track for an oilfield drilling rig and method of installing same. More particularly, the present invention relates to an improved track system which guides a top drive torque assembly substantially parallel to the longitudinal axis of the mast of a drilling rig and the method for installing same.
2. Description of the Prior Art
It is well known in the prior art to use a top drive drilling unit to rotate the drill stem of an oil and gas well. See, for example, U.S. Pat. Nos. 4,449,596; 3,464,507; and 3,766,991. Such a top drive drilling unit is suspended by cable from the crown of a mast of a drilling rig above the drill string. Essentially, the unit rotates the drill string from the top side as opposed to the use of a rotary table, kelly and related equipment at the rig floor.
The use of such a top drive unit requires a track which runs the length of the mast to guide the drilling mast, to restrain it from lateral movement and to transfer torsional loads originating from the rotary drilling operation into the rig. Such torque drive track systems are disclosed in Moses, U.S. Pat. No. 4,865,135 and Richardson, U.S. Pat. No. 5,251,709. However, the use of previously known track systems has several disadvantages. First, it is difficult to assemble and disassemble such track systems due to their configuration and weight. Due to the height of some derricks (over 100 feet), a track system can weigh substantially in excess of 12,000 pounds. Thus, it can be particularly difficult to assemble a prior art track system at a remote location.
Accordingly, there is a need for an improved top drive track system which is simple to assemble and relatively lightweight, and is also capable of providing lateral load restraint and structural rigidity to transfer torsional loads from the drilling unit into the main structural framework of the drilling rig.